feat(policy): add scheduling participant privacy contract

src/govoplan_core/core/policy.py

@@ -5,8 +5,10 @@ from typing import Any, Iterable, Literal, Mapping, Protocol, cast, runtime_chec
 from urllib.parse import quote, unquote
 
 PolicyScopeType = Literal["system", "tenant", "user", "group", "campaign"]
+SchedulingParticipantVisibility = Literal["aggregates_only", "names_and_statuses"]
 
 CAPABILITY_POLICY_PRIVACY_RETENTION = "policy.privacyRetention"
+CAPABILITY_POLICY_SCHEDULING_PARTICIPANT_PRIVACY = "policy.schedulingParticipantPrivacy"
 
 POLICY_SCOPE_TYPES: tuple[PolicyScopeType, ...] = ("system", "tenant", "user", "group", "campaign")
 
@@ -126,6 +128,55 @@ class PolicyDecision:
         }
 
 
+@dataclass(frozen=True, slots=True)
+class SchedulingParticipantPrivacyRequest:
+    """Context for resolving what one Scheduling participant may see.
+
+    ``requested_visibility`` is the Scheduling-owned configuration result. A
+    policy provider may preserve or reduce it, but must not broaden it. Core
+    deliberately defines no fallback when the optional capability is absent;
+    that secure default remains the responsibility of Scheduling.
+    """
+
+    tenant_id: str
+    scheduling_request_id: str
+    participant_id: str
+    requested_visibility: SchedulingParticipantVisibility
+    actor_user_id: str | None = None
+    context: Mapping[str, Any] = field(default_factory=dict)
+
+
+@dataclass(frozen=True, slots=True)
+class SchedulingParticipantPrivacyDecision:
+    """Policy-resolved visibility of other participants' names and statuses."""
+
+    effective_visibility: SchedulingParticipantVisibility
+    reason: str | None = None
+    source_path: tuple[PolicySourceStep, ...] = ()
+    details: Mapping[str, Any] = field(default_factory=dict)
+
+    def to_dict(self) -> dict[str, Any]:
+        return {
+            "effective_visibility": self.effective_visibility,
+            "reason": self.reason,
+            "source_path": [step.to_dict() for step in self.source_path],
+            "details": dict(self.details),
+        }
+
+
+@runtime_checkable
+class SchedulingParticipantPrivacyPolicy(Protocol):
+    """Optional policy hook for Scheduling participant-roster disclosure."""
+
+    def resolve_scheduling_participant_visibility(
+        self,
+        session: object,
+        *,
+        request: SchedulingParticipantPrivacyRequest,
+    ) -> SchedulingParticipantPrivacyDecision:
+        ...
+
+
 @runtime_checkable
 class PrivacyRetentionService(Protocol):
     def privacy_policy_from_settings(self, *args: Any, **kwargs: Any) -> Any:
@@ -160,3 +211,16 @@ class PrivacyRetentionService(Protocol):
 
     def apply_retention_policy(self, *args: Any, **kwargs: Any) -> Any:
         ...
+
+
+def scheduling_participant_privacy_policy(
+    registry: object | None,
+) -> SchedulingParticipantPrivacyPolicy | None:
+    """Return the optional provider without selecting a visibility fallback."""
+
+    if registry is None or not hasattr(registry, "has_capability"):
+        return None
+    if not registry.has_capability(CAPABILITY_POLICY_SCHEDULING_PARTICIPANT_PRIVACY):
+        return None
+    capability = registry.capability(CAPABILITY_POLICY_SCHEDULING_PARTICIPANT_PRIVACY)
+    return capability if isinstance(capability, SchedulingParticipantPrivacyPolicy) else None